Horizontal directional drilling, commonly referred to as HDD, is a process used in a number of applications such as installing utilities underground. The HDD process, regardless of the application, includes a pilot hole-boring step. In this step a bore hole is created that extends underground—generally horizontally or generally parallel to the surface of the earth—starting at a launch point and ending at a termination point.
The bore hole is created by positioning a boring machine to rotate and push a drill string through the ground. A drill bit is attached to the leading end of the drill string. The drill string is created by connecting individual drill rods together end-to-end from a supply of drill rods stored on the boring machine. The connection between the rods is made up, and subsequently broken in a later step, by the boring machine. A typical boring machine includes a gearbox that connects to the drill string, a drill rod storage magazine, and a rod loading mechanism. The rod loading mechanism moves the individual drill rods from the storage magazine into alignment with the drill string and the gearbox where the individual drill rod is connected to and made a part of the drill string.
Rod loading mechanisms typically include a rod transfer mechanism that moves the rod from the storage magazine and positions it with one end in alignment with the drill string and the other end in alignment with the gearbox. The drill rods are typically long, and connection to the drill string requires that the ends of the drill rod be positioned accurately. Thus, the rod loading mechanisms typically include two pipe transfer mechanisms, one on each end of the drill rod, to maximize the accuracy of positioning the respective ends of the drill rod.
When utilizing two mechanisms, however, a drawback arises in that the movement of the two mechanisms is not always synchronized. This may result in misalignment and/or binding. Therefore, there is a need in the art for a method and apparatus for coordinating and synchronizing the rod transfer mechanisms. The present invention overcomes the shortcomings of the prior art and addresses these needs in the art.